Question

Part A:
A coin placed on a turntable rotating at 38.7 rev/min will stay
there if its center is placed no further than 7.2 cm from the axis
of rotation. What is the maximum distance the center of the coin
can be placed from the axis if the turntable rotates at 45.0
rev/min?

Part B:
What is the coefficient of friction between the coin and turntable?